Trackball devices are currently used for a range of input operations, and are often installed in electronic equipment.
One of these conventional trackball devices is disclosed in Japanese Patent Unexamined Publication No. 2002-373055, and is described below with reference to drawings.
FIG. 18 is a perspective view of the conventional trackball device before assembling a mechanical structure and a wiring board. FIG. 19 is a top view and FIG. 20 is a left side view of the trackball device.
A flat part of metal cover 103 with a hole at its center is disposed on roughly cross-shaped resin upper case 101. This cover 103 has first legs 103A respectively hanging down from the first opposing sides of the flat part, and second legs 103C respectively hanging down from the second opposing sides perpendicular to the first opposing sides. Through-hole 103B is provided at the tip of each of first legs 103A. A lower end of each of second legs 103C is extended into caulking lug 103D which extends sideways.
Roughly cross-shaped base 102 is disposed beneath upper case 101. Projection 102A provided on a side face of base 102 is fitted into through-hole 103B on first leg 103A of cover 103 and caulking lug 103D of second leg 103C catches against and is caulked to a side step on base 102 so as to attach upper case 101 and base 102.
A pair of hooks 101A formed into a hook with a downward opening are provided respectively at parts extending sideways to form the rough cross shape of upper case 101. Openings under these hooks 101A configure roller holders 101B. Roughly cylindrical roller 104 is rotatably housed and held in each of roller holders 101B. In total, there are four rollers 104; and two pairs of two rollers 104 opposing each other, when seen from the top, are disposed at right angles to form a square. The lower part of each roller 104 is rotatably held by the top face of base 102. A center part of each roller 104 is roughened and acts as a contact area.
Ring-shaped magnet 105, which is magnetized to north and south poles alternately at a predetermined angle pitch, is coaxially fixed to one end of each roller 104 such that magnet 105 co-rotates with each roller 104. Rollers 104 are disposed such that these magnets 105 are positioned in dents in a cross of upper case 101 and base 102. In other words, each magnet 105 is disposed at a corner of a square formed by rollers 104.
Ball 110, typically made of fluorine-containing rubber, is housed inside the inner space formed by upper case 101 and base 102.
Wiring board 115 is disposed under this mechanical structure, and Hall IC 120, which is a magnetic sensor, and self-resilient push switch 125 with tactile feedback are mounted on the top face of wiring board 115.
Hall IC 120 is provided respectively at a position vertically opposing to each magnet 105. Each Hall IC 120 outputs on and off signals in response to changes in the magnetic flux of each magnet 105 which co-rotates with corresponding roller 104 when roller 104 is rotated.
Push switch 125 is disposed on wiring board 115 at a position corresponding to the bottom part of ball 110, i.e., the center surrounded by Hall ICs 120; and includes a movable contact, fixed contact, and a flat spring for pushing operating ball 110 upward, which are not illustrated.
Upper case 101 forming this inner space has a cylindrical part protruding upward. Upper round hole 101C at an upper end of this cylinder has a slightly smaller diameter than the diameter of ball 110 at the top center of upper case 101. Ball 110, given an upward force by the flat spring, is positioned upward by the rim of this upper hole 101C, and the top part of ball 110 protrudes outward from this upper hole 101C. A predetermined space is secured between ball 110 in this position and the contact area of each roller 104.
When a downward force is applied to this ball 110, the bottom part of ball 110 presses the flat spring of push switch 125 down such that ball 110 is vertically movable inside the inner space formed by upper case 101 and base 102.
Next, the operation of this conventional trackball device is described.
First is described the case when the top part of ball 110 protruding from upper case 101 is touched, typically with a finger, and rotated to the right, left, front, or back in the normal state in which the trackball device is not operated. Ball 110 contacts the contact area of roller 104 which corresponds to the rotating direction, and rotates this roller 104. At this point, other rollers 104 do not rotate, and push switch 125 is also not activated.
In line with the rotation of this roller 104, magnet 105 fixed to this roller 104 co-rotates. This repeatedly makes the north pole and south pole of magnet 105 alternately approach Hall IC 120 opposing to this magnet 105. In response, Hall IC 120 generates a predetermined output.
When ball 110 is rotated in an oblique direction, ball 110 contacts two perpendicularly positioned rollers 104, and rotates both rollers 104. Accordingly, a predetermined output is generated from two Hall ICs 120.
Next, when the top part of ball 110 is pressed typically with a finger, ball 110 pushes down the center of push switch 125, establishing electrical coupling which is a switched-on state.
If the force applied to ball 110 is then gradually released, ball 110 is moved back upwards, propelled by the return of the flat spring of the push switch. Ball 110 stops when it contacts the rim of upper hole 101C of upper case 101, and thus returns to the normal state.
In this conventional trackball device, Hall IC 120 detects the rotation of magnet 105 in noncontact fashion. This is preferable since it ensures a long service life for the roller rotation detecting part. However, expensive Hall IC 120 drives up the price of the device. In addition, there is a need for better performance of the rotation of the ball 110. In particular, tactile feedback is not distinct when rotating ball 110 in the conventional trackball device.